diff --git a/src/Logger/Mail.php b/src/Logger/Mail.php
index 6485b64..57dce3e 100644
--- a/src/Logger/Mail.php
+++ b/src/Logger/Mail.php
@@ -37,7 +37,7 @@ public function __construct($email, $headers = null)
 
         $this->destination = $email;
         $this->type = static::MAIL;
-        $this->headers = $headers;
+        $this->headers = (string) $headers;
     }
 
 }